The present invention relates to semiconductor wafer manufacturing and, more particularly, to cleaning of semiconductor wafers and the like.
A semiconductor wafer, such as those used to fabricate integrated circuit devices, is typically cleaned using a cleaning solution. High frequency, in particular, megasonic, energy may be applied to the cleaning solution. The megasonic energy may have a frequency about twenty (20) times higher than that of an ultrasonic wave that may be used to remove contaminants from the semiconductor wafer.
A megasonic energy cleaning apparatus typically includes a piezoelectric transducer connected to a transmitter. When the piezoelectric transducer is electrically excited and vibrated, the transmitter applies megasonic energy to the cleaning solution in a treating tank. The cleaning solution is agitated by the megasonic energy to cause contaminants to separate from a semiconductor wafer exposed to the cleaning solution. In other words, contaminants attached to a surface of the semiconductor wafer may be vibrated and separated from the surface of the semiconductor wafer by the megasonic energy.
A known type of “wafer cleaning system” using megasonic energy for cleaning is discussed in U.S. Pat. No. 6,039,059 (“the '059 patent”). Such a conventional wafer cleaning system is illustrated in FIGS. 1 to 3, which correspond to FIGS. 1-3 of the '059 patent. Accordingly, a detailed description of the conventional aspects of such a wafer cleaning system will not be presented herein and the '059 patent is incorporated herein by reference in its entirety, including the description therein corresponding to FIGS. 1-3 of the present specification.
Research has been conducted to improve the conventional wafer cleaning system using a megasonic energy cleaning technique or a cavitation phenomenon. However, various limitations have been observed in such research. For example, in a wafer cleaning system having a probe for applying megasonic energy, the probe is generally not cleaned in use, as the probe is withdrawn from a cleaning tub after applying megasonic energy into a cleaning solution in the tub and is removed from the cleaning tub without being cleaned before a subsequent semiconductor wafer is cleaned. If the wafer cleaning system is operated for a long time, contaminants removed from the semiconductor wafer may gather in the probe and the contaminants collected in the probe may re-contaminate a surface of the subsequently cleaned semiconductor wafer during the cleaning operation.